This population of 606 women treated with x-rays for acute post-partum mastitis and their controls (554 sisters; 539 women with post-partum mastitis not treated with x-rays, and their 206 sisters) have been followed by mail questionnaire since 1955. The irradiated women have an increased risk of developing breast cancer. This application proposes continuation of the mail health survey, the review of histopathology of the breast cancers experienced by the treated women and the controls, and periodic mammograhic-thermographic screening of the treated women and eligible controls (NCI guidelines).